Within Clade 1,
the sister-group relationship of Cassiope and Ericoideae is well supported.
The monophyly of Cassiope (11 spp.) is supported by several homoplasious
characters, i.e., Calluna-type pith (char.#8),
lack of bud scales (char.
#9), decussate leaves (char.
#11), fibers absent or poorly developed in leaf midrib (char.
#19), and reduced axillary inflorescences (char.
#29). It is noteworthy that axillary inflorescences are very
uncommon in Clade 1 (Ericoideae + Cassiope), occurring more commonly
in Vaccinioideae (Fig. 12).
Ericoid leaves (char. # 13)
may be an additional apomorphy of Cassiope, but such leaves commonly
occur within Clade 1 (Fig.
13). It is also possible (although less parsimonious) to assume
that ericoid leaves evolved in the common ancestor of Clade 1 or even
in the common ancestor of the core Ericaceae, but the ericoid leaf of
Cassiope differs in morphology from that of Calluna and other ericoid
members of Ericoideae (Stevens 1970). A distinctive synapomorphy of the
species of Cassiope, which was not included in our analyses, is the bisporic
embryo sac. Cassiope is the only member of the Ericaceae known to have
other than a Polygonum type embryo sac (Palser, 1952). The unusual fasciculate
hairs may also be synapomorphic.